Recently, new clean energy systems in which hydrogen is used as an energy medium have been proposed as a countermeasure against global environmental problems due to emission of CO2. Among such energy systems, fuel cell is based on an energy conversion technology of taking electric energy out of hydrogen and oxygen by converting chemical energy, produced when hydrogen and oxygen react with each other to form water, into electric energy. This technology draws attention as the most important next-generation technology to be used as a power source alternative to gasoline engine for vehicles, an on-site electric generator for household use, and a DC power supply for IT (information technology) use.
However, the biggest problems of the hydrogen fuel are storage and transport thereof.
There are various methods have been proposed as method for storing hydrogen. As one of the methods, there is a method of storing hydrogen in gaseous phase into a high-pressure gas cylinder. This storage at high pressure is simple, but requires a container having thick wall. Accordingly, the container is so heavy that the efficiency of storage and transport is poor. Therefore, for example, the application to automobiles is difficult because weight saving counts in automobile manufacture. On the other hand, in case of storing hydrogen in liquid phase, the efficiency of storage and transport is improved as compared to the storage in gaseous phase. However, high-purity hydrogen is required to make the hydrogen in liquid phase and a special container capable of withstanding cryogenic temperature because the temperature of liquefaction process is an extremely low temperature of −252.6° C. That is, there is economical problem. There is another proposal of using hydrogen storage alloy. However, there are problems that the alloy itself is heavy and that, in case of Mg based hydrogen storage alloy having lighter weight, the temperature for emitting stored hydrogen is high near 300° C. There is further another proposal of using porous carbon material such as carbon nanotube. However, there are a lot of problems that the repeatability of hydrogen storage is low, that the storage under high pressure condition is required, that it is difficult to manufacture carbon nanotubes, and the like.
It is an object of the present invention to provide a method of storing hydrogen to be useful as a novel storage and transport method capable of solving the aforementioned problems of the prior art, and capable of achieving the relatively light-weight and stable storage of hydrogen at or near the ordinary temperature and the ambient pressure and allowing easy takeoff of the stored hydrogen.
It is another object of the present invention to provide a hydrogen clathrate to be useful as a novel storage and transport method capable of solving the aforementioned problems of the prior art, and which is relatively light weight and can store hydrogen at or near the ordinary temperature and the ambient pressure and to provide a production method thereof.